Large-scale policies and programs, such as violent crime reduction initiatives and economic development projects, certainly have a substantial influence on population health. Remarkably, the health effects of most policies and programs remain unstudied, particularly those not designed to influence health. Health Impact Assessments (HIAs) are sometimes implemented in an attempt to predict the health effects of a policy before it is adopted. However, actual assessment of the health effects of policies post-implementation is surprisingly uncommon. In the rare circumstance that health effects are studied post-implementation, the choice of design relies on broad guidelines and a new study is mobilized for each assessment. There is thus a critical need for a rigorous and cost efficient system that can be applied regularly to assess the effects of policies and programs on a wide range of health outcomes. The first contribution of the proposed research will be establishment of a new system to determine the health and disparities impacts of policies and programs. The system will comprise a web-based simulation generator to identify the optimal study design and analysis, and a large database of over 10 years of population health data that can be utilized to estimate health effects. The second contribution of the proposed research will be application of this system to assess the health and disparities effects of criminal justice policies and programs in California: specifically a violence program implemented in Oakland, and the criminal justice realignment that was mandated statewide. The establishment of the system overall will be significant because it will revolutionize researchers' ability to regularly and rigorously assess post-implementation health and disparities effects of policies and programs at low cost. The system will be innovative because it challenges the paradigm that pre-implementation HIAs are sufficient, will introduce a new approach to studying policy health effects that is cost efficient, and will incorporate the most rigorous tools from the field of biostatistics (i.e., simulations and causal methods). The web-based simulation generator is significant because it will improve the quality of scientific knowledge on health impacts, and innovative because it moves beyond the current broad guidelines and allows rigorous quantitative assessment of which design and analysis approach is optimal for each program. Preliminary analyses demonstrate the important insight gained by using simulation to optimize study design and analysis decisions. The application of the system is significant because it will provide information about the health and disparities impacts of major changes in criminal justice policies and programs that would otherwise remain unknown. This project overall will have a substantial health impact by improving fundamental understanding of how policies and programs influence health and disparities, reducing the cost while improving the quality of assessments of health effects, and providing the evidence base to inform modification of current policies and design of future policies to protect health and reduce health disparities.